THE THEORY OF WETTING, AND THE DETERMINATION 

 OF THE WETTING POWER OF DIPPING AND SPRAYING 

 FLUIDS CONTAINING A SOAP BASIS. 



By W. F. cooper, B.A. (Cantab.), F.C.S., 

 AND W. H. NUTTALL, F.I.C., F.C.S. 



{From the Cooper Lnborntory for Economic Research, Watford.) 



The dipping of sheep and cattle, as a means of eradicating 'scab,' 

 lice, ticks, etc., and tlie diseases which it is now known the latter may 

 transmit, has met with such success, that compulsory dipping is now 

 in vogue in most pastoral countries. Where compulsory dipping 

 obtains, there must of necessity be some system of the standardisation 

 of dips. In Queensland and South Africa, the respective Governments 

 issue official formulae from which the stockbreeder can prepare his own 

 dipping fluid. Only such proprietary dips, as are duly recognised by 

 the Government, may be employed. In the United States, the regu- 

 lations for the sale of proprietary dips are still more stringent. The 

 quantity of active substance, usually sodium arsenite, nicotine or 

 cresyhc acid, is defined within very narrow limits. Further, no pro- 

 prietary dip is now recognised, unless the manufacturer can furnish 

 a 'Field Tester,' by means of which the stockbreeder can himself deter- 

 mine, in a simple and fairly trustworthy manner, the percentage of 

 active constituent in his bath. 



The underlying idea, upon which all these regulations are based, is 

 that the principal factor, which determines the efficacy of a dipping 

 fluid, is the Cjuantity of toxic substance present. It has been shown, 

 however, in experience derived from field experiments and routine 

 dippings, that this assumption is unwarranted. There is another 

 factor of almost equal importance, viz., the capacity of the dipping 

 fluid to -wet the greasy hide or fleece. A plain aqueous solution of 

 sodium arsenite, containing 1 part of arsenious oxide in 600 parts of 



